1. Technical Field
The invention relates to electronic data capture devices. More particularly, the invention relates to a retrofittable apparatus for converting a substantially planar surface into an electronic data capture device.
2. Description of the Prior Art
Electronic blackboards date at least to the mid-1960s, at which time emphasis was placed on the communication of graphical data, specifically handwriting and sketches, from one location to another. U.S. Pat. No. 3,706,850 discloses a system related to such activity.
At about the same time, graphic tablets that allowed the entry of line drawings into a computer were developed. U.S. Pat. No. 3,838,212 is an early example of developments in this area.
By the mid-1980s, a third kind of a product group was developed to address the need for a local hard copy of material written and sketched onto a dry-erase, so-called whiteboard. This generic group of systems, known collectively as electronic copyboards (ECBs), relates fundamentally to stand-alone devices that have much in common with well known reducing photocopiers.
Each of these devices attempts to provide the user with a natural communication metaphor that uses familiar writing tools. In the case of electronic blackboards and electronic copyboards, the metaphor is a fixed wall-mounted surface meant for mass viewing, in which marking or writing is accomplished by the use of colored markers, and in which erasing is accomplished by wiping the surface with an eraser. In the case of the graphic tablet, the metaphor is a desktop slate and stylus meant for individual use.
Those skilled in the art recognize that both electronic blackboards and electronic copyboards typically require dedicated, highly specialized surfaces and equipment structures. These specialized structures result in an immobile, cumbersome, and relatively expensive system. Systems and approaches generally in this line of technical art are illustrated, for example, in U.S. Pat. No. 3,613,066 to Cecreman, U.S. Pat. No. 4,558,313 to Garwin et al., U.S. Pat. No. 4,506,354 to Hansen, U.S. Pat. No. 4,670,751 to Enokido, U.S. Pat. No. 4,711,977 (Re. 33,936) to Miyamori, U.S. Pat. No. 4,777,329 to Mallicoat, U.S. Pat. No. 4,814,552 to Stefik et al., U.S. Pat. No. 5,248,856 to Mallicoat, U.S. Pat. No. 5,023,408 to Murakami, and U.S. Pat. No. 5,434,370 to Wilson.
The ""066 patent discloses a display panel and means responsive to the positions and moves of a pointer on the panel to generate information signals for a computer. Thin, coherent light beams parallel to the surface of the panel a systematically and repetitively displaced in crossing relation to scan at least part of the surface. The position of a marker relative to the display panel is detected by interference of the marker with the scanned light beams.
The ""313 patent focuses on an indicator-to-data processing interface which employs a light source and a background reflector as constituents in a system to monitor occlusion of light occurring from the positioning and movement of a manually moved indicator over a surface.
The ""751 patent discloses an eraser for an electronic blackboard having a variable erasing area. The eraser includes a small area erasing unit and a detachable large area erasing unit. Detectors determine when the eraser is touched to the surface of the board, as well as whether the small area erasing unit or the large area erasing unit are currently in use.
The ""977 patent discloses an electronic blackboard, writing instrument, and position-detecting control unit. The system uses magnetic bias to detect the position of an writing/erasing element relative to that of video information displayed on a writing surface.
The ""329 and ""856 patents address a graphic input system which employs ultrasound (the ""329 patent) or scanned light (the ""856 patent) to monitor the position of a mobile element over a surface. The ""856 patent includes at least two spaced transceiver-structure stations that optically track the position and motion of a writer or eraser based upon bar code techniques. While it is suggested in the ""856 patent that these transceiver-structure stations may be retrofitted to a conventional writing-surface structure, no discussion is provided for performing such retrofit, nor is it clear that the scanning technology disclosed would be suitable for a retrofit application, where the spaced, separate structures cannot be rendered insensitive to in-use relational changes (for example, movement and vibration of the white board occasioned by movement of the writing implement to and across the surface of the white board during use), and where adequate precision to effect an accurate scan cannot be achieved without regular calibration during use due to the relative positional instability of the multiple spaced sensors.
The ""552 patent discloses an input device, or stylus, for entering hand drawn forms into a computer comprising a writing instrument, a pressure switch doe determining whether the instrument is in contact with the writing surface, an acoustic transmitter for triangulating the position of the stylus on the surface, and a wireless transmitter for transmitting data and timing information to the computer. In operation, the stylus transmits an infrared signal which the system receives immediately, and an ultrasound pulse which two microphones receive after a delay which is a function of the speed of sound and the distance of the stylus from each microphone. From this information the system can calculate the position of the stylus. Switches for indicating functions are mounted on the stylus. Multiple styluses can be used, each transmitting a distinctive identification code so that the system can determine which stylus is the signal source.
The ""408 patent describes an electronic blackboard, including a sensing tablet which senses the position of a writing tool that includes a tuned circuit having a predetermined resonant frequency.
The ""370 patent discloses a graphic data acquisition system in which a digitized record is produced according to the X, Y, and Z position of a writing implement relative to a writing surface. An expanse of electromagnetic radiation is generated in a zone adjacent to the writing surface, and an electromagnetic interactive pen interacts with such electromagnetic radiation to produce a signal that locates the pen relative to the writing surface.
Prior art systems of the type outlined above are relatively complex, immobile, and costly. Typically, they are not readily retrofittable at all, much less to a wide variety of writing-surface structures which are already in hundreds of thousands of users""possessions. In fact, for useful and accurate operation, such systems depend upon a specific surface having either embedded sensors or otherwise precisely predetermined qualities. Further, prior art systems are not particularly adapted to yield information about the condition of a writing stylus or an eraser much beyond its position or station over a writing surface.
Accordingly, it would be advantageous to provide a novel graphic data-acquisition system which offers not only the various features and advantages made available by prior art, but which further effectively addresses the various performance, cost, simplicity, mobility and sophistication issues mentioned above. It would be especially advantageous to provide such a system that is readily retrofitted to existing writing surfaces without the need for special mounting arrangements or regular calibration, while providing a high degree of precision and stability, and while also providing a rich complement of sophisticated features.
The invention is a graphic data-acquisition system which employs a continuously active tracking system to provide a retrofittable apparatus for converting a substantially planar surface into an electronic data capture device. Various techniques are disclosed that allow the fabrication of a retrofittable assembly, such that any substantially planar surface may be converted into an electronic data capture device. Thus, the components of the system are readily retrofittable, at relatively low cost, to a wide variety of otherwise conventional writing-surface structures, such as so-called dry-erase whiteboards.
The invention employs any conventional triangulation technique to track the position and motion of a writer or eraser. As discussed above, many such techniques are known, but these techniques have traditionally required a specialized or dedicated writing surface or have been otherwise unsuited for retrofit to an existing writing surface. The invention exploits to advantage both the significant improvements in modern tracking technology and a novel and improved fitting technique that allows rapid and efficient retrofit of a tracking assembly to a dry-erase whiteboard or other planar surface, while providing a precision tracking system that accurately tracks a writing implement in three dimensions, thus capturing all marks placed on the marking surface.
Further, by using an encoding facility associated with a writing implement the invention provides the ability to distinguish whether the writing implement is used for marking or an as erasing implement, as well as determining the nature or character of written line width or eraser swath, for example specific color in the instance of a colored writing instrument. A data stream thus generated can be used in a variety of ways, such as for example, to feed information into the memory of a digital computer, and/or to feed information for transmission to remote stations for live presentation of writing activity occurring on the writing-surface area in the system.